1. Field of the Invention
This invention relates to a medical tool and a method for the production thereof. More particularly, it relates to a medical tool which, owing to a polymer deposited on the surface thereof, manifests excellent lubricity on being wetted and a method for the production of the medical tool.
1. Description of the Prior Art
Generally, for the manufacture of catheters and other similar medical tools, substances of low friction are adopted as matric materials thereof and further such matric materials are coated with a hydrophilic polymer for the sake of precluding the medical tools from inflicting damage on the inner wall surfaces of blood vessels or on the tissues and enhancing the operability of the medical tools. For example, fluorine resin, polyethylene resin, etc. are used as substances of low friction for matric materials and these matric materials are coated with fluorine resin, silicone oil, olive oil, glycerol, etc.
These measures, however, cannot be expected to impart lasting lubricity to the medical tools. The medical tools which embody these measures have a problem of poor safety in the sense that the lubricious substances are liable to exfoliate, peel, or melt from the surfaces of matric materials.
U.S. Pat. No. 4,100,309 makes a disclosure to the effect that a copolymer of polyvinyl pyrrolidone with polyurethane is used as a substance possessed of lubricity. The method taught by this US patent publication is satisfactory in terms of lubricity and lastingness of this quality. Since this method requires at least two kinds of polymer for coating and essentially necessitates the presence of an isocyanate group as a reactive group on the surface of the matric material, the reaction is not obtainable with either a matric material allowing no easy introduction of the isocyanate group or a polymer possessed of lubricity.
JP-A-59-81,341 also discloses a method for impartation of lubricity similarly by utilizing an isocyanate group on the surface of a matric material.
Further, JP-B-1-55,023 discloses a method for binding a copolymer of polyether, polyamide, or polysiloxane through the medium of polyisocyanate to the surface of a matric material of a medical tool. For this method, the interposition of the isocyanate is an essential requirement and the presence on the surface of the matric material of at least one group selected from among amino group, imino group, carboxyl group, and mercapto group is an indispensable requirement. This method, therefore, is incapable of effecting this binding treatment on a medical tool which is made of polyolefin or halogenated polyolefin and has none of the functional groups mentioned above.
The various methods of surface lubrication mentioned above, however, are not desirable from the standpoint of operability because they require the coating operation to be performed at least twice (as for the coating with a cross-linking compound such as isocyanate and the coating with a lubricious substance) when lasting lubricity must be imparted.
Generally, since a low molecular cross-linking agent (such as, for example, a diisocyanate compound or a diepoxy compound which has a highly active functional groups) is possessed of unduly high reactivity, remains as unreacted monomer which is easy to elute and has toxity, the use of such a substance is not desirable even from the standpoint of safety.
As described above, the impartation of lubricity to the surface of a medical tool imposes a limit on the kind of matric material or requires the coating operation to be carried out twice or more where lasting lubricity is necessary.
An object of this invention, therefore, is to provide a novel medical tool and a method for the production thereof.
Another object of this invention is to provide a medical tool the surface of which acquires lasting lubricity (low friction) on being wetted with body fluid or aqueous solvent, obviates the necessity of carrying out the coating operation twice or more for its own formation, and enjoys high safety and a method for the production of the medical tool.